DE 199 03 939 A1 discloses a self-recovering current limiting device with liquid metal. A pressure-resistant insulating housing is arranged between two solid metal electrodes, in which housing liquid metal is arranged in compressor areas and in connecting channels which are located between them and connect the compressor areas, thus resulting in a current path for nominal currents between the solid electrodes. The current path in the connecting channels is narrower than in the compressor areas. The connecting channels are severely heated when short-circuit currents occur, and emit a gas. Avalanche-like gas bubble formation in the connecting channels results in the liquid metal vaporizing into the compressor areas, so that a flow-limiiting arc is struck in the connecting channels, in which there is now no liquid metal. Once the overcurrent has decayed, the liquid metal can condense again, and the current path is ready to operate again.
WO 00/77811 discloses a development of the self-recovering current limiting device.
The connecting channels broaden conically upwards so that the filling level of the liquid metal can be varied, and the rated current carrying capacity can be changed over a wide range. Furthermore, the offset arrangement of the connecting channels results in the formation of a meandering current path, so that a series of current-limiting arcs are struck when the liquid metal vaporizes as a result of overcurrents. Pinch effect current limiters such as these require a very stable design in terms of pressure and temperature, which involves a complex design. The use of arcs for current limiting results in high wear in the interior of the current limiter, and erosion residues can contaminate the liquid metal. The recondensation of the liquid metal immediately after a short circuit results in a conductive state again, so that no disconnected state is provided.
DE 40 12 385 A1 discloses a current-controlled disconnection apparatus whose functional principle is based on the pinch effect with liquid metal. A single, narrow channel that is filled with liquid metal is arranged between two solid metal electrodes. When an overcurrent occurs, the liquid conductor is drawn together by the pinch effect as a result of the electromagnetic force, so that the current itself constricts the liquid conductor, and disconnects it. The displaced liquid metal is gathered in a supply container, and flows back again after the overcurrent event. The contacts are disconnected without any arcs. However, the device is suitable for only relatively small currents, low voltages and slow disconnection times, and does not offer a permanent disconnected state.
DE 26 52 506 discloses an electric heavy-current switch with liquid metal. On the one hand, a liquid metal mixture is used in order to wet the solid metal electrodes and in order to reduce the contact resistance. In this case, the liquid metal is driven by mechanical displacement, for example by moving contacts or pneumatically driven plunger-type pistons, against the force of gravity into the contact gap. The liquid metal can additionally be stabilized and held fixed in the contact gap by a pinching effect, on the basis of which a current-carrying conductor experiences radial striction as a result of the current flowing through it. External magnetic fields and stray magnetic fluxes, for example resulting from the electrical power supplies, can cause flow instabilities in the liquid metal and are shielded, and may be permitted during disconnection in order to assist the quenching of the arc in the liquid metal. This has the disadvantage that gradual current limiting is not possible, and arcs between the solid electrodes cause oxidation in the liquid metal. The design of the heavy-current switch includes seals for liquid metal, inert gas or a vacuum, and is correspondingly complex.
GB 1 206 786 discloses an electrical heavy-current switch based on liquid metal as claimed in the precharacterizing clause of the independent claims. In a first position, the liquid metal forms a first current path for the operating current and is passed along a resistance element during current switching, and is moved to a second position in which it is connected in series with the resistance element and reduces the current to a small fraction. The heavy-current switch is designed to produce high-intensity current pulses in the megaampere and submillisecond range for plasma generation.